The USC football team hasn't had to go up against many No. 1 quarterbacks playing at full strength.

Virginia's opening day quarterback isn't on the team any longer, Ohio State's quarterback situation was in flux, Oregon's Jeremiah Masoli started the year deep on the Ducks' depth chart, Rudy Carpenter was playing on one leg, and Washington State's Kevin Lopina was even worse off.

Saturday at Arizona Stadium in Tucson, though, the Trojan defense will be tested by a veteran passer, senior Willie Tuitama.

"Willie has been a big, strong thrower since early in his high school days," Carroll said. "He's a really good all-around athlete. He can make all the throws."

Arizona head coach Mike Stoops said Tuitama has thrived as he's become a more reliable quarterback.

"Willie's playing well within himself," Stoops said. "He's taking what the defense is giving him. He's got good command of the offense and playing with poise and confidence, which hasn't always been the case.

Tuitama's play this season is a big reason Arizona (5-2, 3-1 Pac-10) is challenging for the Pac-10 title and on track to play in its first Bowl Game since 1998.

"The biggest thing is we're playing so much more consistently. We continue to mature, and this team has done everything we've asked them to do," Stoops said. "We know that this would be our best group of players, and it's one of the best teams we've had since we've been here."

Tuitama has 1,691 yards on 140 completions in 215 attempts with 15 touchdowns and three interceptions. His 151.4 pass efficiency rating is 19th best in the country and second best in the Pac-10 - behind USC's Mark Sanchez.

Facing a true pocket passes could actually be good for the Trojan defensive line.

"We know he's going to throw the ball, and that means we'll have more opportunity to rush," defensive end Kyle Moore said. ""That's way more fun."

And the defensive line hungry for sacks could cause Tuitama to struggle, Stoops said.

"He understands what they do. He knows their speed. That experience helps him," Stoops said. "It can be very disruptive to your timing, the constant pressure your under. Probably one of the big keys for us is protecting Willie, giving him time to get through a few reads."

While the USC defense will be having fun dealing with Tuitama, the Trojans' offense will have to work against one of the country's best defenses.

Arizona's only allowing 136.5 yards through the air - sixth best in the county.

"Arizona has a disciplined defense against the pass. They're a zone team, and they mix their pressures nicely," Carroll said. "They make it look the field is too small. They're going to keep you in front of them.